Adaptive Front Lighting Systems (AFS) are commonly used to control the intensity and direction of automotive headlamps. An AFS may be used to adjust the angular position of a headlamp to compensate for position changes that occur during acceleration and deceleration of the vehicle. For example, when a car accelerates, the front end of the car may be prone to increasing its angle upward from the road. This increase in angle shifts the beam of the headlamp upward from the road and into oncoming traffic, thereby posing a hazard to other drivers. Furthermore, the horizontal angle of the headlamps may be further affected as the automobile makes a turn. In an AFS system, a motor may be used to control the angular direction of the headlamps, such that the angle of the headlamp is reduced with respect to the road in order to compensate for the increase in angle due to acceleration or due to turning. In many AFS applications, one or more step motors are used to control the position of a headlamp chassis. Some countries, in fact, have mandated the use of such systems for automobiles having high intensity discharge (HID) lamps.
In the event of a failure condition, such as a momentary loss of power, or a shutdown in the motor driver circuit, the position of the headlamp may become fixed in an unsafe position that may pose a danger to other drivers such as dazing or blinding. In some systems, the position of the step motors that position the headlamps are reset and reinitialized after the car is shut down and the key is turned in the ignition.